1. Field of the Invention
The present invention relates to a surgery-assistance apparatus, method and program for assisting doctors in determining excision regions to be removed in surgeries of organs, such as a liver and a lung.
2. Description of the Related Art
When a surgery is performed on a patient to remove a diseased part of his/her organ, such as a liver and a lung, doctors need to appropriately determine a part to be removed, in advance, by performing diagnosis based on images before the surgery. To determine the part to be removed, a method in which a partial region including the diseased part is set and the partial region is determined as an excision region is used. Further, a method in which a dominance region, which is dominated by a part of a structure to be removed, is extracted based on the structure that dominates an organ, specifically, based on the structure that supplies oxygen and nutrition to the organ to keep the normal function of the organ, and the dominance region is determined as an excision region is used.
As the method for determining the partial region including the diseased part as the excision region, Japanese Patent No. 4193201 (Patent Document 1) discloses a method in which a lesion region in a liver is extended, based on the lesion region and plural vessels running in the liver, spherically from the center or the center of gravity of the lesion region toward the outside of the lesion region until the extended lesion region becomes in contact with at least one of the plural vessels, and a substantially circular conic region in contact with the extended spherical region is determined as the excision region.
Further, as the method for determining the dominance region as the excision region, Japanese Unexamined Patent Publication No. 2007-054147 (Patent Document 2) proposes a method in which blood vessels, a liver parenchyma, and a tumor part are extracted from an X-ray CT image of the liver of a patient. Further, a blood vessel that dominates a region to which the extracted tumor belongs is identified based on the positions of the core lines of the extracted blood vessels, the diameters of the blood vessels or the like. Accordingly, a blood vessel that supplies nutrition to the tumor is identified. Further, in the region dominated by the identified blood vessel, a region in which a relative distance between voxels constituting a blood vessel and voxels constituting the liver parenchyma is longer than a predetermined maximum relative distance value is displayed as an abnormal perfusion region that might have been erroneously identified due to a mass effect on the blood vessel or the like.
Here, it is desirable that the excision region is appropriately determined so that a burden of a surgery on a patient and an operation time of the surgery are reduced. For example, it is desirable that the area of the boundary of the excision region is as small as possible to reduce a burden of a surgery on a patient and the operation time of the surgery. Further, it is desirable that the volume of the excision region is minimized so that the healthy normal organ of the patient remains as much as possible. Further, it is desirable to appropriately consider the influence of dominance by the structure to determine the excision region.
However, in the method disclosed in Patent Document 1, the partial region is always determined as the excision region. Therefore, the volume of the excision region and the surface area of excision are larger than the case of determining the dominance region as the excision region in some cases. Further, the influence of dominance by the structure is not considered. Therefore, it is impossible to determine, as the excision region, the dominance region or the partial region that is more appropriate as the excision region.
Further, in the method disclosed in Patent Document 2, the dominance region is always determined as the excision region. Therefore, the volume of the excision region and the surface area of excision are larger than the case of determining the partial region as the excision region in some cases. Hence, it is impossible to determine, as the excision region, the dominance region or the partial region that is more appropriate as the excision region.